You should start taking ovulation tests at around CD 10 (with a regular 28 day cycle). If this if your first time using them maybe start a few days earlier so you can get a better idea of your baseline LH for future reference. I’d suggest testing twice a day, especially your first few months using them because you might have a short surge and could miss it.

Basically, your LH test line will likely be lighter in color than the control line. As you near ovulation, the line should start getting darker. You’ll have a “positive” test as soon as your test line is as dark, or darker than the control line. This is when you know you’re close to ovulation. Your “peak” LH is the day of your darkest line. Usually, you’ll ovulate anywhere from 24-36 hours after your initial positive test, and a peak test indicates you’ll ovulate in 8-12 hours. The initial surge is what is signaling your ovaries to release the egg. You’ll likely see your LH go back down to negative, a light test line, within a day or two of your peak LH. This is because your body has finished signaling the egg to be released. Your fertile days are the 5 days leading up to ovulation, and ovulation day. The most important times to try are once you see that initial surge on your test because that indicates ovulation is happening soon.

I know this is really long, but hopefully that wasn’t super confusing. Here’s also an article I read explaining how for some women cycles opks sometimes show longer surges that plateau, or two surges of LH and what that means for ovulation. The full link to the article can be found here: https://ro.co/fertility/normal-lh-level/#

I found it really helpful to understand why your opks look the way they do. Good luck!

Ovulation strips